The present invention relates to a bicycle according to the preambles of one of claims 1, 30 and 47.
Such a bicycle is known from WO 99/03721. The bicycle described there comprises a pneumatically sprung front fork with two fork arms as well as a pneumatically sprung rear-wheel suspension, each being formed by double-acting pneumatic cylinders. A piston positioned inside the cylinder divides each of the pneumatic cylinders into a first cylinder chamber and a second cylinder chamber. The first cylinder chamber forms a first gas-pressurized spring and counteracts a xe2x80x9cspringing inxe2x80x9d of the fork or of the rear-wheel suspension, respectively, and the second cylinder chamber forms a second gas-pressurized spring that counteracts a xe2x80x9cspringing outxe2x80x9d. The pneumatic cylinders each comprise valves for the separate filling or ventilating, respectively, of the first and second cylinder chambers, which enables a length adjustment or a variation of the xe2x80x9cspring strengthxe2x80x9d, respectively.
DE 298 10 431 U1 discloses a so-called mountain bike that is in particular suited for riding on hilly ground. It comprises a sprung front fork with telescopic fork arms, the length of which is adjustable in steps. Each fork arm comprises a locking pin for fixing the adjusted xe2x80x9cfork lengthxe2x80x9d or xe2x80x9cfork heightxe2x80x9d, respectively. In the interior of the telescopic fork arms, a helical spring is positioned which at least partially buffers shocks that are introduced via the front wheel, and thus improves the riding comfort. The rear wheel is mounted on a swing arm rear suspension that is pivotable around the pedal bearing axis and that is supported toward the frame by a shock-absorbing leg that takes up pressure forces. The shock-absorbing leg is fastened to the frame by means of quick release means, with several xe2x80x9cfastening pointsxe2x80x9d being provided, which enables a step-wise adjustment of the angle between the swing arm rear suspension and the frame, i.e. a step-wise xe2x80x9cheight adjustmentxe2x80x9d of the rear wheel. Due to the individual xe2x80x9cadjustability in heightxe2x80x9d of the front wheel suspension and the rear wheel suspension, an approximately horizontal sitting position can be adjusted both when riding uphill and when riding downhill. It is of advantage in particular when riding downhill that the front wheel is xe2x80x9cextendedxe2x80x9d and the rear wheel is xe2x80x9cretractedxe2x80x9d since this causes the center of gravity to be transferred backwards and the risk of overturning on actuation of the front wheel brake to be reduced. Furthermore, it is of advantage when riding uphill that the front spring element is retracted and the rear one is extended in order to transfer the cyclist""s center of gravity further to the front. The cyclist thus takes up a more relaxed position which increases the efficiency when riding uphill.
DE 41 01 745 A1 discloses a bicycle with a sprung swing arm rear suspension that is connected with the bicycle frame via a resilient spring element, wherein a locking device comprising a cable pull is provided for locking the suspension.
U.S. Pat. Nos. 6,044,940, 2,115,072, and 4,159,105 disclose pneumatic or hydraulic piston/cylinder assemblies that are used as spring or damping elements, respectively.
Furthermore, DE 198 55 161 C1 discloses a height adjusting device comprising a tension spring for adjusting the height of a seat pillar of a bicycle.
U.S. Pat. No. 5,086,866 discloses an off-road motorcycle, wherein the front-wheel and the rear-wheel suspensions can be adjusted in height by means of a hydraulic lifting device, with a pressure generating device being provided for generating a hydraulic pressure. The height adjustment of the front-wheel suspension and the rear-wheel suspension is performed simultaneously, so that the frame remains in a substantially horizontally orientated.
U.S. Pat. No. 4,735,276 discloses a racing motorcycle comprising a front fork that is pneumatically adjustable in height, wherein the fork is completely lowered prior to the start so as to avoid taking off of the front wheel during the starting phase. During riding, the front wheel is pneumatically extended to normal height.
It is an object of the present invention to provide a multi-purpose adjusting device that can be adjusted easily and comfortably, in particular for adjusting the height of the front-wheel suspension, the rear-wheel suspension, the saddle or the steering stem, respectively, of a bicycle.
This object is solved by the features of claims 1, 30 and 47. Advantageous embodiments and further developments of the invention may be taken from the subclaims.
The basic principle of the invention consists in a mechanical adjusting device comprising at least one double-acting piston/cylinder assembly which can be extended xe2x80x9cautomaticallyxe2x80x9d.
In a first basic variant of the invention, at least two adjusting devices are provided, e.g. the height adjusting devices of the front-wheel suspension and of the rear-wheel suspension, which are coupled such that the rear wheel is xe2x80x9cautomatically extendedxe2x80x9d when the front wheel is xe2x80x9cretractedxe2x80x9d, and vice versa.
The adjusting devices for the height adjustment of the front-wheel and rear-wheel suspensions each comprise at least one double-acting piston/cylinder assembly with respective xe2x80x9cplus chambersxe2x80x9d and xe2x80x9cminus chambersxe2x80x9d which are coupled via pressurizing medium lines and at least one shut-off device. For adjusting the riding inclination, the shut-off device is opened. By pressing down the handle bar or by weight transfer of the cyclist, respectively, the piston/cylinder assembly of the front wheel is retracted, this causing the xe2x80x9cfront wheel heightxe2x80x9d to be reduced and the piston/cylinder assembly of the rear wheel to be extended. Pressurizing medium thus flows from the plus chamber of the xe2x80x9cfrontxe2x80x9d piston/cylinder assembly to the plus chamber of the xe2x80x9crearxe2x80x9d piston/cylinder assembly and from the minus chamber of the rear piston/cylinder assembly to the minus chamber of the front one. The xe2x80x9cplus circuitxe2x80x9d and the xe2x80x9cminus circuitxe2x80x9d may have approximately equal pressures.
Vice versa, by pressing down the frame in the rear section, the piston/cylinder assembly of the rear wheel can be retracted and the piston/cylinder assembly of the front wheel can be extended, this elongating the front fork and the range of spring. After the adjustment has been effected, the shut-off device will be closed again.
According to a further development of the invention, the piston/cylinder assemblies and the pressurizing medium lines are filled with a gas, e.g. with air. The piston/cylinder assemblies then additionally serve as xe2x80x9cpneumatic shock-absorbing legsxe2x80x9d, this increasing the riding comfort, in particular during off-road uphill or downhill riding.
In accordance with a further development of the invention, a locking device is provided for locking the piston/cylinder assembly of the rear wheel. Optionally, a corresponding locking device may also be provided for the piston/cylinder assembly of the front wheel. The locking device may, for instance, be a double-acting hydraulic cylinder that is integrated into the housing of the piston/cylinder assembly intended for height adjustment, and that is e.g. filled with oil. Two chambers of the hydraulic cylinder are connected with one another via a hydraulic line and a shut-off device, wherein xe2x80x9chydraulicxe2x80x9d locking is possible by shutting off the shut-off device. As an alternative to a double-acting hydraulic cylinder, a mechanical locking device may also be provided. The hydraulic cylinder also may have one chamber only which is connected with a hydraulic reservoir via a check valve.
According to a further development of the invention, one shut-off device is provided in each of the two pressurizing medium lines that connect the piston/cylinder assemblies. Preferably, these tow shut-off devices can be actuated by a common actuator. Furthermore, one single actuator may be provided for the shut-off devices and the locking device. Furthermore, both pressurizing medium lines may be connected with one another via a bypass line that can be shut off, so as to compensate the pressure in both pressure circuits.
In accordance with a further development of the invention, a spring element is provided at the front-wheel suspension and/or at the rear-wheel suspension. Springiness may be achieved by pneumatic piston/cylinder assemblies and/or by separate or additional spring elements. The spring means of the front-wheel and/or the rear-wheel suspensions thus can be xe2x80x9cdecoupledxe2x80x9d from adjusting devices. In the case of xe2x80x9cseparatelyxe2x80x9d provided spring means, the height adjustment could also be effected hydraulically. As spring elements, e.g. compression springs or elastomer elements may be used. The mechanical spring elements may also be integrated into the piston/cylinder assembly of the front-wheel or rear-wheel suspensions, respectively. A spring element may, for instance, be incorporated into the plus chamber of the piston/cylinder assembly. In the case of strong shocks, where the xe2x80x9cpneumaticxe2x80x9d range of spring is made full use of, an additional mechanical spring effect thus can be achieved. Alternatively, an arrangement outside the piston/cylinder assembly is also possible.
According to a further development of the invention, a filling/draining valve is provided for filling or draining, respectively, the piston/cylinder assemblies or the pressurizing medium lines, respectively. The filling valve may be a check valve that opens with a predetermined pressure only, wherein the pressure can be adjustable. The xe2x80x9cpneumatic spring strengthxe2x80x9d thus can be adjusted in accordance with the weight of the cyclist and the desired riding comfort. Preferably, a compressed-air reservoir, e.g. a compressed-air cylinder, is provided, which may be integrated in the bicycle frame, which is very space-saving. Additionally, a compressed-air generator may be provided, which is preferably arranged such that ambient air is sucked in and pressed into the compressed-air reservoir or the piston/cylinder assemblies, respectively, by springing in of the front wheel or of the rear wheel, respectively. A compressed-air generator functioning according to the principle of an air pump may, for instance, be used.
In accordance with a further development of the invention, the bicycle comprises a fork, wherein both fork arms each are formed by a piston/cylinder assembly. The rear wheel may be mounted on a swing arm rear suspension that is connected with the frame via a lag hinge and the piston/cylinder assembly for height adjustment of the rear wheel.
In a second basic variant of the invention, two cylinder chambers of the piston/cylinder assembly that are separated from each other by a piston, i.e. a xe2x80x9cplus chamberxe2x80x9d and a xe2x80x9cminus chamberxe2x80x9d, can be connected with one another via a fluid channel, this causing a pressure compensation to be effected.
At one of the two sides of the piston, a piston rod is fastened, which stands out from the piston/cylinder assembly and can be shifted axially. Thus, the size of the effective piston area of the plus chamber differs from the effective piston area of the minus chamber, namely by the cross-sectional area of the piston rod. Due to the differing sizes of the effective piston areas, a xe2x80x9cdifference forcexe2x80x9d on the piston or the piston rod, respectively, results even when the pressure in the two cylinder chambers is equally high, which enables an automatic extending of the adjusting devices.
In a third basic variant of the invention, effective piston areas of different sizes are also allocated to the two cylinder chambers, but the cylinder chambers here are permanently separated from one another by the piston. Furthermore, a locking device for locking the piston is always provided in this basic variant. This variant thus is particularly suited as adjusting device for a saddle or a steering stem, respectively, of a bicycle, where mechanical locking is absolutely necessary.
The adjusting device according to the invention can be used for many purposes, e.g. for the height adjustment of the front-wheel suspension, the rear-wheel suspension, the saddle or the steering stem. A substantial advantage consists in that the adjusting device is automatically extendable by pressure energy that is stored in the piston/cylinder assembly.